Simplify the following expression: $\sqrt{125}-\sqrt{5}-\sqrt{20}$
Explanation: First, try to factor any perfect squares out of the radicals. $= \sqrt{125}-\sqrt{5}-\sqrt{20}$ $= \sqrt{25 \cdot 5}-\sqrt{5}-\sqrt{4 \cdot 5}$ Separate the radicals and simplify. $= \sqrt{25} \cdot \sqrt{5}-\sqrt{5}-\sqrt{4} \cdot \sqrt{5}$ $= 5\sqrt{5}-\sqrt{5}-2\sqrt{5}$ Finally, simplify by combining the terms. $= ( 5 - 1 - 2 )\sqrt{5} = 2\sqrt{5}$